This invention relates to inflatable bladders, and, more particularly, to an inflatable bladder which includes an internal brace which causes the inflated bladder to conform to the body of a wearer.
The invention finds particular utility in buoyancy compensators. A buoyancy compensator is worn by an underwater diver for adjusting the buoyancy of the diver depending upon the diver's depth below the water level. Examples of buoyancy compensators are described in U.S. Pat. Nos. 4,990,115, 5,011,334, and 5,046,894.
A buoyancy compensator or B.C. generally includes a bladder which provides an inflatable chamber. The chamber is inflated with air or other gases to provide buoyancy.
Buoyancy compensators include single bag and double bag devices. A double bag B.C. uses a nylon fabric shell that is sewn separately and assembled with a free standing polyurethane bladder inserted inside of the nylon shell. The bladder serves as the air holding component of the system, and the shell serves to control the form of the inflated bladder.
A single bag B.C. is constructed from a composite material that incorporates a polyurethane film laminated or bonded to the back of a nylon fabric. This composite simultaneously forms the shell and the bladder similar to a double bag but a single layer material and a single construction technique. Essentially, the bladder becomes the outer shell.
As a result of its inherent construction, single bag B.C.'s often rely on internal braces or stays that restrict and control the expansion of the bladder as it is inflated with air. The normal techniques used for these braces are either a 3 dimensional stay, which is a separate "tube" of composite material that is welded or bonded to the walls of the bladder, or a 2 dimensional stay, which bonds the front wall of the bladder directly to the back wall. Both of these techniques produce a straight or rectilinear bladder form. To a certain degree, a 2 dimensional stay will constrict the bladder in each joint area and allows the sides of the bladder to bend when an external force is applied. However, a two dimensional stay still relies on the external system to create conformity and produces only hard angles instead of a curved surface.